Sciences des matériaux
Structural, microstructural and magnetic properties of 1% Fe-doped ZnO powder nanostructures prepared by mechanical alloying.
ZnO powder nanoparticles were doped with iron (mixing produced by mechanical alloying). Their structure, microstructure and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). ZnO starting pure powder exhibits a hexagonal crystal structure with space group P63mc.Otherwise, with the addition of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. The size of crystallites and microstrains were milling time-dependent. Voir les détails
Mots clés : microstructure; ZnO; mechanical alloying; XRD; SEM-VSM.
Structural modification, photoluminescence, andmagnetic property enhancement with Er3+ doping,of sol–gel TiO2 thin films
Nanocrystalline undoped and Er3+ doped TiO2 thin films were prepared by sol–gel dip-coatingtechnique onto glass substrates. Post-deposited films were annealed at 450 °C for 1 h. Differentialscanning calorimetric analysis showed that undoped film crystallization occurred at 339 °C, whileit appears at lower temperature for Er:TiO2. X-ray diffraction and Raman spectroscopy resultsindicate that the films crystallize only into anatase phase, and the crystallite size decreases from24.3 to 21.16 nm with increasing Er3+ doping ratio. The photoluminescence (PL) spectra arecomposed of two broad peaks at 520–570 nm and 640–680 nm assigned to (2H11/2, 4S3/2)–4I15/2 and4F9/2–4I15/2 transitions of Er3+ ions, respectively. PL emission intensities increase gradually raisingthe erbium doping ratio. Vibrating sample magnetometer results of undoped TiO2 thin films reveala ferromagnetic behavior at room temperature and erbium doping leads to an enhancement of thesaturated magnetic moment (Ms). Voir les détails
Mots clés : TiO2 doped Er3+, Sol–gel, Photoluminescence, Magnetic Properties
Characterization of The Structure, Microstructure of ZnO Powder Nanostructures as Transparent Ceramic for Optical Applications
ZnO powder nanoparticles have been studied to investigate their structural and microstructural properties using X-ray diffraction (XRD)and optical microscope for examined ZnO pure powder. The ZnO powder exhibited a hexagonal crystal structure with space group p63mc of ZnO, XRD patterns of powder ZnO were obtained from the full pattern XRD using the MATCH program. For the applications of Zinc oxide as transparent ceramic for optical applications, ZnO is a potential candidate material for optics applications, which has attracted considerable attention over past decades due to its wide potential applications. Voir les détails
Mots clés : ZnO, microstructure, XRD, Optical Microscope.
Etude du composrtement à l'endommagement des materoaux composites stratifiés
Dans ce travail, plusieurs composites stratifiés à matrice époxyde ont fait l’objet d’une étude expérimentale dans le but de déterminer l’influence de certains paramètres tels que, le type de renforts, la séquence d’empilement et l’hybridation sur le comportement mécanique et dynamique amortissant. Une étude détaillée est d’abord menée pour déterminer les propriétés mécaniques des différents composites stratifiés, en traction statique et en flexion 3-points. Les résultats obtenus ont été analysés et comparés à ceux trouvés par la méthode ultrasonore. Des observations microscopiques au microscope optique et au microscope électronique à balayage (MEB) des faciès de rupture des différentes éprouvettes ont été présentées et les modes d’endommagement ont été analysés. Ensuite, une analyse du comportement dynamique, en utilisant la méthode d’analyse dynamique mécanique (DMA) et la méthode d’analyse modale expérimentale (EMA), est mise en place pour identifier les propriétés viscoélastique et dissipatives des différents matériaux. Enfin, l’utilisation de la méthode d’analyse modale et la méthode ultrasonore (propagation des ondes de Lamb) pour la détection de la présence d’endommagement a permis d'éclairer le lecteur sur la sensibilité de ces deux méthodes d’analyse, et de mettre en évidence l’évolution des propriétés mécaniques de la structure composite en fonction du niveau de dégradation. Voir les détails
Mots clés : Composites stratifiés, Comportement viscoélastique, Interface, vibrations, Analyse modale, amortissement, Cohésion, endommagement
Analyse par spectroscopie Infrarouge à transformée de Fourier et diffraction des rayons X d’un matériau composite.
Les composites à matrice polymère sont utilisés en général comme des biomatériaux à cause de leurs constituants. Le matériau analysé est un composite à matrice en polymère renforcé par une fibre de verre utilisé comme prothèse orthopédique d’un tibia. Les résultats obtenus de diffraction des rayons X et spectroscopie Infrarouge à transformée de Fourier(FTIR) montrent la présence de la silice SiO2 et de l’alumine Al2O3 se sont parmi les constituants de la fibre de verre ainsi que la présence des molécules organiques se sont parmi les constituants de la résine polyester. Voir les détails
Mots clés : composite, Prothèse orthopédiques, DRX, FTIR.
Study and analysis of mechanical and viscoelasticbehavior in flexure of laminated composites
In the present paper, seven laminated composites were thesubject of an experimental study to determine their mechanical and viscoelastic properties by means of dynamic mechanical analysis in a bending configuration. The influenceof the frequency, fiber type and fiber orientation on dynamic mechanical properties of different system composites were investigated. Carbon/epoxy laminates exhibit agreat stiffness when fibers are oriented along the axis ofthe clamps, and the maximum modulus was reported forunidirectional carbon/epoxy laminate [08 plies] with56.4 GPa. The glass transition temperature was found to decrease with the incorporation of fibers and increase with increased frequency. For the Kevlar/epoxy laminate, an increase of 12.5 8C in glass transition temperature wasobserved. This is related to a better interfacial adhesion between epoxy matrix and Kevlar fibers Voir les détails
Mots clés : Composite laminate, Dynamic mechanical analysis, Fiber/matrice interface, glass transition temperature
Effect of cold rolling on the recrystallization of 904L austenitic stainless steel
The aim of this work is to study the recrystallization in the 904L austenitic stainless steel, which underwent a cold rolling with two different deformation amounts (50 and 90%). DSC tests have been conducted to determine the temperature range of the recrystallization. It was found that reducing the deformation amount slightly delays the recrystallization. The microstructure of the as-received alloy consists of austenitic grains recognized by the twins they contain. The deformation induced a corrugated microstructure with the presence of ribs. The XRD analysis confirmed that only γ phase peaks were present in the as-received alloy and showed that the deformation induced the extinction of γ phase peaks and the apparition of α phase peaks. Voir les détails
Mots clés : recrystallization, 904L, Cold rolling, DSC
Etude des propriétés mécaniques et électrochimiques d'un multi-matériau fonctionnel obtenu par rechargement dur base Ni-Cr-Fe
La corrosion et l’usure dans un milieu de refroidissement complexe et agressif étant très compliqué, ce travail a pour objectif, en plus du fait de réaliser deux bi- matériaux (25CD4/ Inconel 182) par deux modes de rechargement dur différent , Shielded Metal Arc Welding (SMAW) et le Tungstène Inerte Gaz (TIG Pulsée), de caractériser l’assemblage sous trois formes différentes : Microstructurale, Mécaniquement et par des mesures électrochimiques en mettant l’accent sur la protection cathodique et les critère de protection du couplage galvanique 25CD4/Inconel 182. Deux étapes essentielles ont été réalisées, à savoir ; La réalisation des bi-matériaux par rechargement SMAW et TIG Pulsée et la caractérisation mécanique et physico-chimique des composés, particulièrement, l’étude électrochimique en milieu marin (3,5% de NaCl) à la température ambiante en tenant compte de l’un des moyen de protection le plus utilisé dans l’industrie : la protection cathodique. Voir les détails
Mots clés : tig pulsée, inconel182, rechargement, corrosion, Protection cathodique
CHARACTERIZATION OF IRON ORE AND SCALE FOR SYNTHESIZING VINYL PAINT
As part of the development of iron ore deposits in Algeria and a concern for the preservation of the environment, we are planning to characterize two materials for a possible synthesis of vinyl paint in this study. Iron ore is a red iron oxide pigment with an oolitic structure containing phosphorus. The second material is a steel by-product (scale) that should be recycled. This study covers the characterization of these two components through Chemical analysis, Particle size analysis, Thermal analysis (TGA, DSC), the Observation by SEM, X-Ray Diffraction analysis and Spectrophotometric analysis. Chemical analysis showed that the pigment contains 53.18% of total iron and mostly the gangue is dominated by silica and alumina. Scale in turn contains 73.83% of iron in the form of iron oxides (FeO, Fe3O4 and Fe2O3). Grinding tests illustrated that the scale is much more suitable for grinding than pigment. The granulometric analysis gave a volume distribution of the particles with a size between 0.7 and 32 µm for scale and 0.6 to 40 µm for the pigment and their specific areas are 1.6 and 1.5 m2/g. TGA and DSC showed that the iron pigment loses weight with phase dissolution by consuming energy when the temperature increases. Scale gains weight by the formation of a new phase with heat. Scanning electron microscope of red iron pigment showed a grain aggregate formed rounded over at least iron oxide and gangue. The EDS analysis illustrated a predominance of iron with four predominant oxides in the case of iron ore deposits. Chemical elements forming these four oxides are silicon, calcium, aluminum and magnesium. The SEM of scale showed a homogeneous structure composed of sizes of iron oxide grains and shapes ranging from 1 µm to 10 µm. X-ray diffraction analysis showed that the iron in the pigment is in the form of hematite (Fe2O3) and goethite (FeO(OH)). A tiny portion is combined with silica as fayalite (Fe2SiO4). The iron in the calamine is in the form of the three oxides (FeO, Fe2O3 and Fe3O4). Spectrophotometric tests showed that both materials have virtually no absorption and maximum reflection (100%) in the visible range Voir les détails
Mots clés : Pigment iron, scale (calamine), Simultaneous thermal analysis, X-ray diffraction, Spectrophotometry
STUDY OF STRUCTURAL , OPTICAL AND ELECTRICAL PROPERTIES OF ZnO THIN FILMS PREPARED
ABSTRACTIn this work, we studied deposited Cobalt- doped ZnO thin films via dip-coatingtechnique onto glass substrate, Zinc acetate dehydrate, cobalt acetate, 2-methoxyethanol andmonoethanolamine were used as starting materials. The obtained thin films here characterizedby X-ray diffraction, UV- visible absorption, Atomic force microscopy (AFM). It is foundthat all the thin films have good crystallinity and a preferential orientation o f crystallitesalong [002] axis of ZnO with wurtzite structure. The AFM have provided the information onmorphology of this films where the size grain and average surface roughnes (Rms). Voir les détails
Mots clés : Thin films, ZnO, Cobalt, Dip-Coating, XRD, AFM, UV-Visible absorption.